1. Field of the Invention
The present invention relates to a method for diagnosing a valve of a fluid supply line, and to a computer program set up for this purpose.
2. Description of the Related Art
Different fluids may be provided in the fresh-air suction line of an internal combustion engine. For example, the crankcase in an internal combustion engine is able to be ventilated, and this ventilation can be rerouted to the fresh-air suction line of the engine (in particular into an induction manifold of the combustion engine). In addition, exhaust-gas recirculation lines are known, via which combustion gases are returned to the suction line of the combustion engine.
Such supply lines are able to be monitored with the aid of diagnoses. For example, published German patent application document DE 10 2008 041 804 A1 describes the diagnosis of an exhaust-gas recirculation system. The idea of this method is to use a pressure ratio within the air supply section (that is to say, the pressure upstream from the throttle valve versus the pressure downstream from the throttle valve) or between the air supply section and the exhaust-gas section (i.e., the intake manifold pressure versus the exhaust-gas recirculation pressure) or via a position of a throttle valve of the intake manifold in order to determine whether an adverse effect (especially sooting) is manifesting itself in the exhaust-gas recirculation system. To do so, the mentioned values of the pressure differential are compared to a reference value.
Published German patent application document 10 2008 002 721 A1 discloses the diagnosis of a ventilation system; in this case an error of the ventilation system can be detected through a brief interruption of the ventilation line between the crankcase and the air system of the combustion engine, and by monitoring the Lambda value of the exhaust gas of the combustion engine.
Published German patent application document DE 10 2009 002 746 A1 proceeds from a method for checking the operativeness of a tank ventilation system of a motor vehicle which is equipped with an internal combustion engine providing charge detection, based on the intake manifold pressure. The tank ventilation valve is opened in defined manner and/or actuated in closing manner, and the operativeness of the tank ventilation valve is inferred from the intake manifold pressure that comes about in the process.